Flare fittings are a type of compression fitting used with metal tubing, usually soft steel, ductile (soft) copper and aluminum, though other materials are also used. Tube flaring is considered to be a type of forging operation, and is usually a cold working procedure. During assembly, a flare nut is used to secure the flared tubing’s tapered end to the also tapered fitting, producing a pressure-resistant, leak-tight seal. Flared connections offer a high degree of long-term reliability and for this reason are often used in mission-critical and inaccessible locations.
Flared fittings are appropriate alternatives to solder-type joints when the use of an open flame is either not desired or impractical. Copper tube used for propane, LP, or natural gas may use flared brass fittings of single 45°-flare type, according to NFPA 54/ANSI. Z223.1.
Flare fittings consist of a body with a flared or coned end. Special flaring tools are used to install the tube to fit inside the flared end, providing a deep seal. Flare fittings can handle higher pressures and a wider range of operating parameters than standard compression fittings.